What if there are no usb slot in 20 years? I cannot rule out this possibility.
You will simply plug the floppy disk adapter in the matrix /tesla /ohmibod whatever their name will be in 20 years slot
That's what adapters are for!
I really dont know.
If you look at the image in the OP post the USB stick seems functional.
Maybe the author only wanted to avoid this scenario. Or keep really simple, as said. That was his choice, not mine.
I only noted that he scrapped the need to rely on an hypothesis (the possibility to use an USB stick) going to the simplest yet more reliable form of storage.